[ELLs] GEOLOGY OF THE OTTAWA PALÆOZOIC BASIN 103 
affect both the thickness and distribution of the several divisions to a 
considerable degree. 
The definition of several of these faults, some of which are appar- 
ently important breaks, was carefully observed. Others are appar- 
‘ently local, and affect only the members of one formation. The 
heaviest line of fracture, which is that south of Ottawa city, extending 
northward to the rear of the city of Hull, affects all the members of the 
Paleozoic series from the Potsdam to the Medina. The larger faults 
appear to be of two kinds. Some are vertical displacements of the 
strata, while others are more of the nature of horizontal throws. In the 
case of the latter the movement appears fo be connected with the later 
intrusions seen in the Montreal district, which resulted in the forma- 
tion of the eruptive masses found in the area east of the St. Lawrence 
and also in the Montreal mountain. Along the lower Ottawa these 
hills are seen on both sides of the lake of Two Mountains, in the peaks 
known as Mount Calvaire on the north side of that sheet of water, and 
in Rigaud mountain on the south side. 
Throughout the entire Ottawa basin there has evidently been an 
enormous amount of denudation. This is evidenced by the deep sound- 
ings which have been noted in certain parts of the present channel of 
the Ottawa itself, and by the presence of old channels in the vicinity 
of the present river course, most of which are now filled up with great 
deposits of clay and sand. Among the deepest soundings which have 
been reported from the present channel of the river is that taken in 
the lower part of what is styled the Deep river, about twenty-five miles 
west of Pembroke. Here the river from the foot of the Rapides des 
Joachims, for nearly thirty miles, follows a narrow channel, with high 
cliffs on the north side, while on the south side the country is compara- 
tively low for some miles. Near the lower end of this stretch a bold 
headland, styled Oiseau rock, rises boldly to a height of about 450 feet 
above the river at its base, while a sounding made by means of a rope 
near the foot of the cliff is reported as giving a depth of 410 feet, and 
in the middle of the river, opposite, about 500 feet. The depth of this 
stretch of river, about ten miles éast of des Joachims Rapids, is said to 
be even greater. The elevation of this part of the Ottawa river, above 
mean tide level at Quebec is 370 feet, so that the bottom of this depres- 
sion in the river channel is about 130 feet below sea level. 
At the foot of the Deep river the Ottawa has left its former channel 
and now bends sharply to the south. The old channel, which evidently 
continued in a direct line eastward, is now choked up with great masses 
of sand and gravel. 
